Artificial legs having knee joints, commonly referred to as above-knee prosthesis, are well known and understood. A variety of such prosthetic devices have been described in the available literature and many styles and types are commercially available.
Preventing the giving way of the knee when in stance phase is of critical importance for trans-femoral prosthetic device users in order to prevent the user from falling down. In this regard, various kinds of artificial knee joints that perform stance phase control, including load brake knee, have been put into practice to prevent the giving way of the knee. However, none of the known devices that have been used to prevent the giving way of artificial knee joints are capable of controlling knee movement at any bending angle. An object of the present invention is to provide a trans-femoral prosthetic device that allows the user to prevent the artificial knee from giving way at any and all bending angles.
Another limitation of known above-knee prostheses is their inability to allow the user to ascend and descend stairs and slopes using a reciprocating gait. Some known prosthetic devices incorporate a mechanism that facilitates a reciprocating gait while descending stairs and slopes. When the user rests his or her weight on the prosthesis while bending (flexing or extending) the artificial knee, the resistance of knee bending is increased causing the bending to slow. While suitable for descending stairs and slopes, these devices cannot enable a reciprocating gait when ascending stairs or slopes. It is a further object of the present invention to provide an above-knee prosthesis that facilitates a reciprocating gait close to normal while both ascending, and descending, stairs and slopes.
Also known are trans-femoral prostheses having knee joints that employ sensors able to detect muscle contractions of the thigh stump in conjunction with hydraulic or pneumatic systems to control knee joint resistance. Such devices require a specialized socket to receive the thigh stump, adding to the system's complexity and overall cost. A further object of the present invention is to provide an above-knee prosthesis that functions to control knee joint resistance at all knee joint angles, without the use of electronic controls, that is simple in design, and can be produced and employed at modest expense.